Effect of an external responsive neurostimulator on seizures and electrographic discharges during subdural electrode monitoring

Purpose: Approved neural-stimulation therapies for epilepsy use prolonged intermittent stimulation paradigms with no ability to respond automatically to seizures. Methods: A responsive neurostimulator that can automatically analyze electrocortical potentials, detect electrographic seizures, and rapidly deliver targeted electrical stimuli to suppress them was evaluated in an open multicenter trial in 50 patients, 40 of whom received responsive cortical stimulation via subdural electrodes implanted for epilepsy surgery evaluations. Results: Four patients, ages 15 to 28 years, monitored at three institutions, with clinical and electrographic response to neurostimulation, are described. Electrographic seizures were altered and suppressed in these patients during trials of neurostimulation lasting less than or equal to8 h, with no major side effects. In one patient, stimulation appeared also to improve the baseline EEG. Conclusions: Responsive cortical neurostimulation may be a safe and effective treatment for partial epilepsy. This information was derived from a small group of patients in an observation study. A double-blind, controlled Food and Drug Administration (FDA)-approved study of a permanently implanted responsive neurostimulation system to treat medically refractory partial seizures is under way.